The problems of corrosion and attendant effects such as pitting have troubled water systems for years. For instance, scale tends to accumulate on internal walls of various water systems, such as boiler and cooling systems, and thereby materially lessens the operational efficiency of the system. In this manner, heat transfer functions of,the particular system are severely impeded.
Corrosion is a degradative electrochemical reaction of a metal with its environment. Simply stated, it is the reversion of refined metals to their natural state. For example, iron ore is iron oxide. Iron oxide is refined into steel. When the steel corrodes, it forms iron oxide which, if unattended, may result in failure or destruction of the metal, causing the particular water system to be shut down until the necessary repairs can be made.
Typically in cooling water systems, corrosion along with pitting has proven deleterious to the overall efficiency of the cooling water system. Recently, due to the popularity of cooling treatments using orthophosphate to promote passivation of the metal surfaces in contact with the system water, it has become critically important to maintain relatively high levels of orthophosphate in the system to achieve the desired passivation without resulting in fouling or impeded heat transfer functions.
Environmental regulations have begun to impose increasingly more severe restrictions on the discharge of phosphate from industrial processes into local rivers and streams. Phosphates originally evolved as a viable alternative to zinc based industrial water system treatment programs which were severely restricted due to their high toxicity to fish and other aquatic life.
Recent environmental regulations in the Great Lakes area restricts the discharge-of phosphorus (P) to a maximum of 1 ppm. Current industrial corrosion technology fails to meet these severe discharge limits. These programs rely greatly on the effective corrosion inhibiting properties of inorganic and organic phosphate combinations at levels far in excess of the 1ppm P discharge limit.
It is an object of this invention to provide industrial water users with an effective corrosion inhibiting treatment program which complies with environment standards for the discharge of less than 1 ppm P.